A packaging structure is known in which a first substrate including a copper terminal and a second substrate including a copper terminal are stacked, and in which the copper terminals are directly bonded (so-called a Cu—Cu direct bonding).
For Cu—Cu direct bonding, a method in which surfaces of the copper terminals to be bonded are activated and in which the surfaces of the copper terminals are bonded under vacuum pressure (room temperature bonding, SAB: Surface Activated Bonding), a method in which the surfaces of the copper terminals are grinded by a tool grinder or the like and in which the copper terminals are bonded under reducing atmosphere at vacuum pressure, a bonding method by generating metal salt or the like, is used.
Here, before performing the Cu—Cu direct bonding, it is necessary to align the copper terminals to be bonded. For a method of aligning the copper terminals before bonding, a first method is known that uses an apparatus including an alignment device provided in a vacuum chamber, for example.
Further, a second method that is called hybrid bonding is known. According to this method, a copper terminal formed on a first substrate is sealed by semi-cured resin, and a front end side of the copper terminal and a surface of the resin are grinded or polished so that the heights of the copper terminal and the resin become equal. Similarly, a copper terminal formed on a second substrate is sealed by semi-cured resin, and a front end side of the copper terminal and a surface of the resin are grinded or polished so that the heights of the copper terminal and the resin become equal. Then, the second substrate is provided on the first substrate such that the front end sides of the copper terminals face with each other, and the first substrate and the second substrate are temporarily fixed by contacting surfaces of the semi-cured resins. Thereafter, the copper terminals are directly bonded (Cu—Cu directly bonded) by thermal compression bonding and the semi-cured resins are completely cured.
Patent Document 1: Japanese Laid-open Patent Publication No. 2015-008228
However, by the above described first method, the apparatus that includes the alignment device in the vacuum chamber is expensive, and corrosion of the alignment device may occur as well.
Further, by the second method, there may be a problem that the resin may be inserted between the copper terminals when temporarily fixing the copper terminals or directly bonding the copper terminals, and the connection reliability between the copper terminals is lowered.